1. Field of the Invention
The present invention relates to an evaporator that is provided in a fuel cell system and that evaporates raw fuel liquids, and particularly to an evaporator raw fuel injection apparatus that offers improved evaporating efficiency for raw fuel liquids.
2. Description of the Related Arts
Recent years have seen accelerated development of fuel cells for fuel cell-equipped automobiles provided with fuel cell systems, because of their environmental friendliness in generating electrical energy. One such fuel cell system is the so-called methanol-reformed fuel cell system. This fuel cell system employs, for example, a mixture of water and methanol as the raw fuel liquid, and is equipped with a fuel evaporator that evaporates the raw fuel liquid and supplies raw fuel gas to a reformer. For autothermal reformers, reforming air including oxygen-containing gas such as air is mixed with the raw fuel gas evaporated by the fuel evaporator, and supplied to the reformer.
As an example of a fuel evaporator provided in a conventional fuel cell system, the fuel evaporator described in Japanese Patent Application No. Hei 11-125366 by the present applicant will be explained with reference to FIG. 8. As shown in FIG. 8, the fuel evaporator 100 evaporates raw fuel liquid FL in an evaporating chamber 110 with high temperature heating gas HG generated in a combustor (not shown), producing evaporated raw fuel liquid FL (hereunder referred to as xe2x80x9craw fuel gas FGxe2x80x9d). In addition, the fuel evaporator 100 supplies the raw fuel gas FG produced by the evaporating chamber 110 to a superheating chamber 120 where it is superheated by the heating gas HG exiting from the evaporating chamber 110. The evaporating chamber 110 and superheating chamber 120 are connected by a guide conduit 130 formed along the floor 110A of the evaporating chamber 110. The evaporating chamber 110 houses a plurality of U-shaped heat medium tubes 111, 111 . . . that conduct the heating gas HG to the inside, and the heating gas HG is conveyed from the heat medium tubes 111, 111 . . . through the guide conduit 130. The fuel evaporator 100 injects the raw fuel liquid FL from the raw fuel injection apparatus 140 toward the heat medium tubes 111, 111 . . . The raw fuel liquid FL injected from the raw fuel injection apparatus 140 contacts with the heat medium tubes 111, 111 . . . so that it undergoes exchange with the heat received from the heating gas HG and is evaporated. The fuel evaporator 100 supplies the raw fuel gas FG produced by evaporation of the raw fuel liquid FL into vapor tubes 121, 121 . . . situated in the superheating chamber 120. The fuel evaporator 100 also supplies the heating gas HG discharged from the heat medium tubes 111, 111 . . . into the superheating chamber 120 through the guide conduit 130. Thus, the raw fuel gas FG flowing through the vapor tubes 121, 121 . . . is superheated by the heating gas HG fed into the superheating chamber 120. Also, the fuel evaporator 100 then discharges the superheated raw fuel gas FG from the vapor tubes 121, 121 . . . and feeds it to a reformer (not shown). In an autothermal system, air is usually fed in between the fuel evaporator 100 and the reformer as reforming air by air compressor (not shown). This air and the raw fuel gas FG produced in the fuel evaporator 100 are mixed and supplied to the reformer.
However, if the raw fuel liquid is not adequately atomized, dispersed and contacted with the heat medium tubes 111, 111 . . . the exchange efficiency for exchange with the heat received from the heating gas HG will be lower, thus reducing the evaporation efficiency. This will cause the unevaporated raw fuel liquid FL to accumulate in the evaporating chamber 110, creating liquid pools. The evaporation efficiency is particularly reduced in cases of contact with low temperature areas of the heat medium tubes 111, 111 . . . or adhesion of liquid droplets of the flying raw fuel liquid FL onto the inner wall 110B and elsewhere in the evaporating chamber 110. Yet, since the raw fuel injection apparatus 140 injects the raw fuel liquid FL from the fuel injection nozzle (not shown) in only one fixed direction at a prescribed injection pressure, it is not possible to achieve adequate atomization or dispersion of the raw fuel liquid FL, while the injecting direction of the raw fuel liquid FL cannot be adjusted.
It is therefore an object of the present invention to provide an evaporator raw fuel injection apparatus which accomplishes adequate atomization and dispersion of the raw fuel liquid and evaporates the raw fuel liquid with high efficiency.
The evaporator raw fuel injection apparatus according to the invention which solves the aforementioned problems is characterized in that, in an evaporator having an evaporating chamber in which raw fuel liquid is evaporated by a high temperature heating medium, there are provided a first injection portion that injects the raw fuel liquid into the evaporating chamber, and a second injection portion that injects gas or liquid with a prescribed directional property into the raw fuel liquid injected from the first injection portion.
According to this evaporator raw fuel injection apparatus, a air stream is created by the gas or liquid injected from the second injection portion, and this stream atomizes and disperses the raw fuel liquid injected from the first injection portion into the evaporating chamber. Thus, evaporation of the raw fuel liquid is promoted by the heat received from the high temperature heating medium, for improved evaporation efficiency.
This evaporator raw fuel injection apparatus is characterized in that the second injection portion injects the injected gas or liquid in a swirling current.
According to this evaporator raw fuel injection apparatus, generation of a swirling current by the gas or liquid injected from the second injection portion can achieve greater atomization and dispersion of the raw fuel liquid injected from the first injection portion, thus providing even better evaporation efficiency.
The evaporator raw fuel injection apparatus is also characterized by being provided with three or more of the first injection portions, and being provided with a second injection portion that injects gas or liquid only into the raw fuel liquid injected from the first injection portions at both ends.
According to this evaporator raw fuel injection apparatus, the second injection portion is constructed to generate the stream only at the areas surrounding the evaporating chamber that have low evaporation efficiency, and this simple structure therefore allows evaporation of raw fuel liquid at a high efficiency.
The gas or liquid having a prescribed directional property is a gas or liquid injected in different fixed directions in order to generate a given air stream from the gas or liquid injected from the second injection portion. According to this embodiment, as shown in FIG. 6, air with different directional properties is injected from an air injection portion provided with air injection nozzles and air injection conduits in a construction suited for each air stream, in order to generate a swirl current (vortex), bent current, deflected current or offset current as the stream. For example, for a swirl current, the air is injected from four air injection nozzles and the direction of each air injection is the direction toward the adjacent air injection nozzle.